The US Ambassador to Malta, Douglas Kmiec, a key conservative supporter of President Obama, resigned his post last week following a State Department Office of Inspector General’s report accusing him of spending too much time writing and speaking about his own Roman Catholic beliefs rather than on embassy business.

According to the Associated Press, Kmiec says he was not pushed out, but in his resignation letter he slams “the middle ranks” of the State Department who he says have since restricted his activities.

“My actions have been confined to the ministerial. You deserve better, but until these rigid, and rigidly narrow, perspectives are overcome, you and the President are being deprived of the intelligent insight of much of your Embassy’s work,” he wrote in a letter to Secretary of State Hillary Clinton over the weekend.

Ambassador Kmiec, a well-known conservative commentator, originally supported Republican Mitt Romney’s bid for president in 2008 but became a key Catholic supporter of Barack Obama after Romney dropped out. He was nominated as Ambassador to Malta in July 2009.

The State Department IG report earlier this month determined Kmiec’s “outside activities have detracted from his attention to core mission goals” at the embassy.

“An unfortunate OIG report published last week claims that high standard unmet on the unsupported speculation that someone doing as much writing as I have done could not have also been devoted to the embassy mission. The contrary proof, Madame Secretary, is in the strength of our embassy. Our work is careful, thorough, and timely, and I am fully apprised of all of it, and of course, fully supported by men and women of great dedication and ability,” he wrote to Secretary Clinton.

Ambassador Kmiec suggested in his resignation letter that the Inspector General’s criticism of his work was payback for a 1989 position he took while working the Office of Legal Counsel, in which he argued the IG’s work must be limited to investigating waste, fraud, and abuse.

“That opinion stung the OIG and I suspect I have just experienced a “sting-back,”” he wrote.

Kmiec’s resignation is effective August 15 or, as he put it in his resignation letter “on the feast of the Assumption, 2011.”